Measurement of nuclear spin relaxation time in lanthanum aluminate for development of polarized lanthanum target

TL;DR

This study measures the nuclear spin relaxation times in lanthanum aluminate doped with neodymium to evaluate its potential as a polarized lanthanum target for neutron experiments, finding promising long relaxation times at low temperatures.

Contribution

It provides the first detailed measurement of $T_1$ times in lanthanum aluminate doped with neodymium under various magnetic fields and temperatures, informing polarized target development.

Findings

$T_1$ can reach up to 100 hours at 0.1 K and 0.1 T.

Longer $T_1$ times are achievable at lower magnetic fields and temperatures.

The results support the feasibility of using this material for neutron spin experiments.

Abstract

The nuclear spin-lattice relaxation time ($T_1$) of lanthanum and aluminum nuclei in a single crystal of lanthanum aluminate doped with neodymium ions is studied to estimate the feasibility of the dynamically polarized lanthanum target applicable to beam experiments. The application of our interest is the study of fundamental discrete symmetries in the spin optics of epithermal neutrons. This study requires a highly flexible choice of the applied magnetic field for neutron spin control and favors longer $T_1$ under lower magnetic field and at higher temperature. The $T_1$ of $^{139}{\rm La}$ and ${}^{27}{\rm Al}$ was measured under magnetic fields of $0.5$-$2.5$ T and at temperatures of $0.1$-$1.5$ K and found widely distributed up to 100 h. The result suggests that the $T_1$ can be as long as $T_1 \sim$ 1 h at $0.1$ K with a magnetic field of $0.1$ T, which partially fulfills the requirement of the neutron beam experiment. Possible improvements to achieve a longer $T_1$ are discussed.